variation and evolution - evidence for evolution: fossils

Question 1

what are fossils?

Answer 1

remains or organisms from millions of years ago which are found in rocks

Question 2

how are fossils formed

Answer 2

• form when parts of organisms haven’t decayed. this can happens when conditions for decay are absent for example temp too cold, not enough oxygen or water
• form even if parts of the organism are slowly replaced by minerals during the decay process
• be preserved traces of organisms (footprints, spaces where roots were)

Question 3

problems with fossils?

Answer 3

• many of the earliest forms of life were soft-bodied organisms. didn’t have shell or skeleton meaning they very rarely formed fossils. even if they did, they were destroyed by rocks in earth’s crust.
• due to little amount of fossils for early life, scientists can’t be certain how life on Earth began

Question 4

what do fossils show?

Answer 4

• a huge number of species have become extinct. this means there are no remaining individuals of that species still alive

Question 5

reasons for species becoming extinct?

Answer 5

• due to a catastrophic event (asteroid colliding with earth)
• environment changes (weather patterns or new disease or predator killing all species)
• new, more successful species evolves and competes with it (scarce food or water)